Developments of a long liquid scintillation detector for fast neutron time-of-flight experiments

We have developed a long NE213 liquid scintillation detector (LLSD, 80 cm x 6.5 cm X 10 cm) which is useful as a position sensitive detector and a high-efficiency neutron detector for measurements of neutron emission cross sections. LLSD is a long rectangular shaped NE213 scintillator coupled with two photomultipliers at both ends of the scintillator cell. Position information along the long cell axis is obtained by the time difference method. The time compensated signal needed for time-of-flight (TOF) experiments is provided by a mean timer. Data are acquired for TOF, position and pulse-height signals gated by n-gamma discriminator signals using a three-parameter data acquisition system. The updated data acquisition system and a position-dependent biasing analysis could achieve a remarkably lower bias level down to similar to 1 MeV neutrons with good n-gamma discrimination compared to the similar type NE213 detectors and remove position dependence of detection efficiency. LLSD with the sophisticated data taking and processing techniques proved to be very effective for neutron emission cross section measurements for 10-18 MeV incident neutrons as a wide-angle scattering detector and a high-efficiency single detector.